It is known that chickens and turkeys cannot be slaughtered, defeathered, killed and packed for freezing directly upon the processing line without a period of aging, usually for about eight hours, intervening between the freezing of the fowl and the earlier stages of treatment. Other animal products also require such aging and the need for the aging step has proved to be a handicap in efforts to process meat in a single processing line in a continuous manner to the frozen stage. Furthermore, the toughness associated with rigor mortis may only be attenuated by an aging stage.
The need for the aging step which, in the case of chickens, turkeys and the like, requires the fowl or the parts thereof to be processed, to be placed in bags or other containers and stored for periods of up to eight hours, is that rigor mortis sets in some 21/2 to 3 hours after slaughter, giving rise to a progressive toughening of the meat. The meat, if prematurely frozen, will remain tough when defrosted and the chemical processes of rigor can interfere with the cooking process and, of course, with the taste and texture of the meat.
To avoid the effect of rigor mortis on the toughening of the muscle, an aging or holdover step has been required heretofore to allow the chemical processes associated with rigor mortis to fully subside and permit the muscle to return to a tender state, before packing or further processing.
In the following discussion, reference will be made to the processing of chicken by way of simplifying the description. However, the principles of this invention are applicable wherever aging has been required following the fresh slaughter of the animal to avoid the toughness associated with the chemical processes of rigor mortis in the muscle tissue of the piece of meat. The invention is applicable, therefore, not only to chickens, but also to other fowl including turkey, to parts thereof such as turkey breasts, and to other meat which, like ham, may require substantial aging before further processing, freezing or packaging in its final form for distribution to the consumer. The invention may be used, moreover, to avoid the aging of fresh-killed meat wherever the aging is inconvenient for the on line processing thereof.